Method of making internal combustion engine cylinder made of an aluminum alloy enriched with a wear-resistant component on the inside surface



United States Patent Inventor Tokichi Izumi,

Kawagoe-shi, Japan Appl. No. 823,585

Filed May 12, 1969 Patented Oct. 27, I970 Assignee Izumi Automotive Ind., Co.

Kawagoe-shi, Saitama Ken, Japan a corporation of Japan Priority May 14, 1968 Japan 43/32372 METHOD OF MAKING INTERNAL COMBUSTION ENGINE CYLINDER MADE OF AN ALUMINUM ALLOY ENRICHED WITH A WEAR-RESISTANT COMPONENT ON THE INSIDE SURFACE 1 Claim, 2 Drawing Figs.

U.S.C1 164/114, 123/193 Int. Cl 822d 13/00 Field of Search 164/1 14,

55-59; 123/193 (Consulted), 193(C): 75/148: 92/169 [56] References Cited UNITED STATES PATENTS 2,005,175 6/1935 Adams 164/114 3,333,579 8/1967 Shockley etal 123/193 OTHER REFERENCES Metals Handbook ASM 8th Ed, Vol 1, Published by ASM, Metals Park, Novelty Ohio, pp. 952, 953 and 882, 890. Primary Examiner-J. Spencer Overholser Assistant Examiner-V.K. Rising A!t0rney Polachek and Saulsbury ABSTRACT: This disclosure relates to an internal combustion engine cylinder characterized in that it is made of a centrifugally cast high silicon aluminium alloy in which the silicon content is made high in the inside part but low in the outside part and is a process for the manufacture of the same characterized in that the high silicon aluminum alloy is centrifugally cast at a high temperature of more than 200C. higher than its liquidous temperature of the alloy.

Patented Oct. 27, 1970 FIG,2

I N VENTOR um I 7'? TTURVE 5 7bkich-i I Z METHOD OF MAKING INTERNAL COMBUSTION ENGINE CYLINDER MADE OF AN ALUMINUM ALLOY ENRICHED WITH A WEAR-RESISTANT COMPONENT ON THE INSIDE SURFACE The present invention relates to an internal combustion engine cylinder made of an aluminum alloy enriched with a wear-resistant component on the inside surface and method of making the same. Particularly, the present invention relates to an internal combustion engine cylinder made of an aluminum alloy in which the content of a wear-resistant component is high on the inside surface but is low on the outside surface in a single casting and a method of making the same.

An aluminum alloy is low in the strength at high temperatures but is so light and is so high in the thermal conductivity that its use for internal combustion engine parts is increasing at present.

It is well known that particularly silicon contained in such aluminum alloy reduces the high thermal expansion which is the greatest defect of the aluminum alloy, decreases its wear and further rather improves its heatproofness and that therefore an aluminum alloy containing silicon is extensively used for internal combustion engine parts, especially pistons.

It is being considered recently to use an aluminum alloy having such excellent performance for cylinders. That is to say, now that pistons are being extensively made of an aluminum alloy, it is much to be noted to adopt cylinders made of an aluminum alloy having a similar thermal expansion cocfficient.

However, when a large amount of silicon is contained in an aluminum alloy to improve the wear-resistance, there will result defects that the thermal conductivity will be lost and the toughtness will be impaired. Therefore, various investigations are being made to use an aluminum alloy for cylinders.

An object of the present invention is to provide an internal combustion engine which has an improved wear-resistance without a loss of thermal conductivity and an impairment of toughness and which is made of an aluminum alloy in which the content of silicon is high on the inside surface but is low on the outside surface in a single casting.

An another object of the present invention is to provide a process for making the above internal combustion engine by a centrifugal casting.

As a result of my long investigations on aluminum alloy castings for internal combustion engines to attain these objects, I found that these objects can be attained by providing an aluminum alloy cylinder in which the content of silicon for improving the wear-resistance is made high only on the inside surface particularly requiring a wear-resistance but is made low on the outside surface to improve the thermal conductivity and toughness.

in order to explain the influences of silicon on the thermal conductivity, thermal expansion coefficient. toughness and wear-resistance, the influence of silicon content on physical properties of an aluminum alloy is shown in Table 1.

TABLE 1.INFLUENCE OF SILICON CONTENT ON PHYSICAL PROPERTIES OF ALUMINUM ALLOY Content of Si, percent 1 By a dry sliding friction test.

As shown in the above Table l, silicon improves the thermal expansion coefficient and wear-resistance. That is to say, the alloy high in the silicon content is low in the thermal conductivity and toughness but is high in the thermal conductivity and toughness, and the alloy low in the silicon contentis low in the thermal expansion coefficient and wear-resistance. As in the above, in an aluminum alloy or particularly an aluminum alloy to be cast, the silicon content particularly has a great in fluence on its physical properties.

The present invention is based upon the ingenious adoption of the above influence of silicon on aluminum alloy.

A feature of the present invention is an internal combustion engine cylinder characterized in that it is made of a centrifugally cast high silicon aluminum alloy in which the silicon contentis made high in the inside part but low in the outside part.

Another feature of the present invention is a process for the manufacture of the internal combustion engine cylinder made of a centrifugally cast high silicon aluminum alloy in which the silicon content is made high in the inside part but low in the outside part characterized in that the high silicon aluminum alloy is centrifugally cast at a high temperature of more than about 200C. higher than its liquidous temperature of the alloy.

lnherently, when silicon (specific gravity: 2.4 is added to aluminum (specific gravity: 2.7), both will perfectly dissolve with each other in a molten state but will have only a slight solubility in a solid state and will be separated from each other.

In the present invention, in order to utilize such property, an aluminum alloy containing a large amount of silicon is poured into a centrifugal casting machine and is rotated at a high revolution speed. Then silicon having a lower specific gravity 1 than that of aluminum will be deposited more in the inside part. Thus, in the structure of the obtained casting, it is shown that free silicon is more in the inside part and that the silicon content is far lower in the outside part.

For example, when the high silicon aluminum alloy containing 22.3 percent Si, 2.40 percent Cu. 0.7 percent Mg, l.l percent Ni, 0.l percent Zn, 0.21 percent Mn and the remainder Al is centrifugally cast at the temperature of 950C. in the revolution speed of 2,000 rpm. to manufacture a cylinder having an inner diameter of 79 mm., outer diameter of mm. and length of 245 mm., the content of above metals in the inside and outer parts is as shown in Table 2.

TABLE 2.-ALLOY COMPOSITION Composition (percent) Si Cu Mg Ni Fe Zn Mn Al 0. 7 l. l 0.6 0.10 0.21 Best. 0. 9 0. 9 0. 4 0. 08 0. 20 D0. 0. 5 1.2 0. 7 0. 18 0. 21 Do.

As evident from the above mentioned Table 2, due to the centrifugal force in casting, the silicon content is high in the inside part but is far lower in the outside part.

An internal combustion engine cylinder made of a centrifugal casting of an aluminum alloy in which the silicon content is thus high in the inside part but low in the outside part is high in the wear-resistance particularly on the inside surface, is high in the thermal conductivity and toughness on the outside surface and has a very excellent performance.

inherently, in an aluminum alloy which is high in the silicon content, the silicon is so strong in the tendency to proeutectically crystallize that, if a material high in the thermal conductivity is used for the casting mold or the mold temperature is low, the silicon content will become high in both inside and outside parts. Therefore, unless a mold which is low in the thermal conductivity and high in the temperature is used, the object of the present invention will not be attained.

Though the specific gravity difference between aluminum and silicon is 0.3, with a melt at a low temperature near the liquidous temperature of the alloy, the viscosity is so high and the required centrifugal force is so large that, in working the panying drawings in which: I

. present invention, it is necessary to properlyselect such condiv tions as the mold condition. melt temperature and the number of revolutions or centrifugal force of the mold in the eentrifugal casting. As a result of many tests, in order to make the present invention mostv effective. the centrifugally casting mold had betterbe of a sand or refractory which is comparatively low in the thermalconductivity and it is necessary that the ,melt temperature should be about 200C. above the liquidous temperature of the alloy, that is, about 800 to 950C;

and the number-of revolutions'of themold should be more than about 2,000 rpm. t I

Further, in the present invention, when a high silicon alu:

minum alloy is 'castqcentrifug ally, as already detailed, there will be obtained a centrifugally cast cylinder in which the silicon content is higher in the inside part than in the outside part andan engine cylinder made by working such centrifugally cast cylinder will have a very excellent performance.

The product according to the present invention is not only adapted to such a thing requiring a high performance asparticularly a cylinder for internal combustion engines but can be also extensively applied to any other similar thing 'or to any case wherein the compositions of the inside part and outside part must be made different from each other.

in the cylinder thus manufactured, the silicon content of the inside part was 21 .93 percent and the silicon content of the outside part was 21.88 percent. Therefore the silicon content of the inside part was almost not different from that of the outside part.

The cylinder thus manufactured does not give the object,

function and effect of the cylinder of the present invention.

EXAMPLE3 (Control) Example 1 was repeated except that the casting temper'ature was 900C. and the revolution speed was 2,000 r.p.m.

in the cylinder thus manufactured, the silicon content of the inside part was 22.02 percent; and the silicon content of the outside part was 21.98 percent, but it was recognized that the object, function and effect of the present invention were not so good.

EXAM PLE 4 Example 1 was repeated e'xceptthat'the casting tempera ture was 870C, therevolution speed was 2,000 rpm. and the high silicon aluminum alloy containing 18.0 percent Si; 2.20

, percent Cu, 0.6 percent Mg. 0.8 percent Ni, 0.5 percent Fe,

0.10 percent Zn, 0.20 percent Mn and the remainder Al was used.

;The present invention is further illustrated by the following nonlimitive examples taken in connection with the a'ccom- FIG. 1 shows a microscopic structure of the internal combustion engine cylinder. of the presentinvention in which the silicon content is high; and g g FIG, 2 shows a microscopic structure of the outside partof the internal combustion engine cylinder of the present inven- 1 tion in which the silicon content is low EXAMPLE 1 The high silicon aluminum alloy containing 22.3 percent Si, I 2.40 percent Cu, 0.7 percent Mg.l.l percent Ni, 0.6 percent Fe,'0.l0 percentZn, 0.21 percentMn and the remainder AI.

was centrifugallycast at the temperature of 950C. in. the

revolution speed of 2,000 rpm. to manufacture a'cylinder having an inner diameter of 79 mm., outer diameter of H5 mm.andlength of245 mm.

. in the cylinder thus manufactured. the silicon content of the higher than its liquidous temperature toprovide an inside part EXAMPLE 2 (Control) Example 1 was repeated except that the casting temperature was 820C. and the revolution speed was 2,000,r.p.m.

EXAMPLES Example I was repeated except that the casting temperature was 860C, the revolution speed was 2,000 rpm. and the high silicon aluminum alloy containing l.l.8 percent Si, l.30 percent Cu, 0.8 percent Mg, 1.4:percent Ni, 0.5 percent Fe,

0110 percent Zn, 0.l5 percent Mn and the remainder Al was used.

In the cylinder thus manufactured. the silicon content of the inside part was l5.0l percent and the silicon content'of the outside part was 9.85 percent.

1'. A process of the manufacture of the internal combustion engine cylinder made of a eentrifugally case high silicon aluminum alloy in which the silicon content is made high in the inside part but low in the outsidepart. which consists of first rotating the alloy with the large amount of silicon in a centrifugal castingmachine at ahigh temperature of more than 200C.

and then depositing silicon having the lower specific gravity thanthe specific gravity of the aluminum in the preparedinside part of the rotated molten mass. f

in the cylinder thus manufactured, the silicon content of the inside part was 20.68 percent and the' silicon content of the outside part was l4.55 percent. 

